Preheat the oven to 180°C/350°F. Butter three 20cm (8in) round cake pans. Line the bottom of each with a round of parchment paper and butter the paper.
Combine the flour, 1 ¾ cups (350g) of the sugar, baking powder, salt and poppy seeds in the large bowl of an electric mixer. Beat on low speed to blend the ingredients and break up any lumps, about 30 seconds. Add the butter, lemon zest and 1 cup of the buttermilk to the flour mixture. Beat on low – be careful, the flour may fly everywhere – until completely mixed. Raise the speed to medium and beat for 1-2 minutes to lighten and aerate the batter.
In a medium bowl, combine the egg whites with the remaining ¼ cup buttermilk; whisk to blend thoroughly. Add this mixture to the batter in 2-3 additions, scraping down the sides of the bowl and beating only enough to incorporate. Divide the batter among the prepared pans.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes.
While the cakes are cooling, make the lemon syrup: in a small nonreactive saucepan, combine the remaining ¼ cup (50g) of sugar, the lemon juice and the water. Bring to the boil, stirring to dissolve the sugar.
Turn out the cake layers onto wire racks and generously brush them hot lemon syrup over the warm cakes to moisten evenly. Let cool completely.

Make the frosting: split the vanilla beans lengthwise and scrape the seeds into the sugar with the back of a knife. In the large bowl of an electric mixer, beat the cream cheese and butter on medium speed until light and fluffy. Gradually add the sugar, 1 cup at a time, beating well after each addition and scraping down the sides of the bowl. Continue to beat until very fluffy, 3-4 minutes. Add the vanilla extract and beat well.

Assembling the cake: place one cake layer, top side down, on a cake plate and spread about a fifth of the frosting over the cake to cover evenly. Repeat with the second cake layer + another fifth of the frosting, then place the third layer on top. Frost the top and sides of the cake with the remaining frosting. Garnish with whatever strikes your fancy.

My birthday was last week and my blog's "birthday" is coming up next week. Great similarities :)Happy blog-anniversary Patricia! I wish you many many years of baking and cooking inspiration! You are always spoiling us with your wonderful creations and we want more!

I'm glad that I've found your blog and always amaze by your creative and continous baking activities. One thing I really like about is that you always put convertion measurement of the recipes which really really helpful for me since we in Indonesia used to have the grams instead of cups or ounce for measuring.

Once again congratulations and I hope you can share with us many more recipes in years to come!